Polyacrylonitrile fiber behavior. I. Mechanisms of tensile response

✍ Scribed by Shlomo Rosenbaum

• Publisher: John Wiley and Sons
• Year: 1965
• Tongue: English
• Weight: 619 KB
• Volume: 9
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1965.070090606

✦ Synopsis

The behavior of polyacrylonitrile fibers has been studied by a number of methods over a wide range of temperatures. At the glass transition temperature T,, in the vicinity of 100°C. by linear thermal expansion, creep, and dye sorption experiments, the break extension was found to rise abruptly, while an initial, stiff response disappeared. The tensile recovery as normally measured was incomplete at all temperatures; below T,, however, all extensions were completely reversible when the kinetic conditions for retraction were provided. The main extension below T, is attributed to the straightening of twisted molecules against the intramolecular repulsion of adjacent dipoles, the small initial extension up to the "yield" knee to an increase in volume required for the operation of the main response. The additional extension(s) above T, appear(s) to involve permanent relative displacement of fiber elements. Water depressed T, by 30-35°C.